Is the phone "new" or have you had a "new" touchscreen installed?
If the phone is new and as you still have the problem after performing a factory reset then I suggest that you consult the warranty statement, found in the user guide that came with the phone, as to what you have to do to make a claim for a manufacturer's warranty repair/replacement for your phone.
If it is only the touchscreen that is new you should go back to whoever replaced the screen and tell them of your problem. If you replaced it yourself then I suggest that you go back and check your work, looking for loose screen/digitizer flex cable connections for example.
Hopefully this is of some help.
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